1. Field of the Invention
This invention relates to an apparatus for exchanging a tool of a bending machine and, more particularly, to an apparatus for readily exchanging a thin reverse die disposed at the center of a split die row in a bending machine for automatically altering an upper die length.
2. Description of the Prior Art
As fields employing panels formed by bending the four sides of work sheet are recently increased, a bending machine of the type having a split upper die capable of altering in its upper die length responsive to the length of the work has been used different from a bending machine or the type for exchanging the upper die by avoiding the interference with a U-shaped rise of the side edge of the work (e.g., the edge of the short side) previously bent at its edges so as to bend the other side edge of the work (e.g., the edge of the long side). When a number of split upper dies (hereinafter referred to as "split dies") of the same length are closely contacted to form a series of upper dies in the split die type bending machine, the bending machine cannot be adapted for altering the work length since the work length altering step takes a pitch of one split die. To this end a bending machine having several types of split dies of different lengths is prepared to cope with the different work lengths in combination with the split die group has been known.
Since the above-described bending machines all have inserted the split dies to the grooves on the lower end of a ram by a manual work when altering the die length to clamp the dies thereto, it takes a long time to change the die length. Then, another bending machine in which split dies hung from the grooves of the lower end of a ram are moved by a proper NC control system, a plurality of reversible thin split dies (hereinafter referred to as "reversible lower dies") are attached to the central portion of the split die group of standard length and the reversible dies of the necessary number are risen or reversed by the NC to automatically alter the die length and retract the dies to thereby working various shapes in one machine has been proposed.
A bending machine or a press brake exchanges a die whenever altering the bending angle and/or the bending shape of a work sheet. In this case, the die is exchanged not only from an upper die of certain angle to another upper die of different angle but also from the upper die to a goose-neck die, or vice versa. As above mentioned, since a reversing mechanism in the press brake having reversible dies is associated at a position approaching from a back gauge on the rear wall of a ram to other unit, it is easy to exchange the dies of a standard split die group from each other or the die to the goose-neck die, but it is very difficult to exchange the reversible dies. Therefore, in the actual working, the working necessary to exchange the dies should be executed by other press brake or a folding machine by avoiding the die exchange. Thus, there arise drawbacks that one bending machine or press brake should originally operate various workings but other machines should be employed on separate working lines.
An object of the present invention is to provide an apparatus for readily exchanging reversible dies of a bending machine having upper die length altering function.
Another object of the present invention is to provide an apparatus for accurating controlling the number of reversible dies.